#include <stdio.h>
#include <math.h>
#define LOCAL
int main()
{
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    long long n, m;
    int count = 1;
    double sum = 0;
    while (scanf("%d%d", &n, &m) ==2 && n*m)
    {
        // printf("%d %d\n",n,m);
        sum = 0;
        for (int i = 0; i + n <= m; i++)
        {
            sum += 1 / pow(n + i, 2);
        }
        printf("Case %d: %.5f\n", count, sum);
    }
    return 0;
}